In the oil industry, heavy oil pumped to the surface contains various components besides the oil itself. Such components include salt water, sand and fine clays. Typically they are pumped into a production tank and a demulsifying chemical is added to aid in the separation of water from the oil. In this separation process, the sand and fine clays settle to the bottom with the sand retaining a residual amount of oil which can vary from about 10% to 40% or more. This mixture of sand and oil is known as oil slop. Water is also bonded to the oil in the slop, thus making the actual volume of sand in the oil slop between about 30% to 50% or less.
Substantial costs are associated with the disposal of oil slop material. Companies are charged a per cubic meter fee for their disposal. The costs are greatly reduced when the oil content of the material is low, since this results in a reduction of the volume of material to be disposed of, in addition to presenting environmental benefits. A variety of processes have been developed to remove oil from the sand.
Currently as a standard procedure in the industry, high pressure water is pumped into the oil slop contained in a production tank servicing the oil well. This process is known as “stinging” the oil well. The water is pumped into the oil slop material through a long wand at a pressure as high as 2500 pounds per square inch. The process makes the oil slop material sufficiently viscous so that it may easily flow from the tank into a vacuum truck. One of two steps is then taken. First, the oil slop material may be taken to a cleaning facility which incorporates heat, mechanical agitation and use of chemicals to separate the oil and water from the sand. This process is quite costly, since it requires not only the initial handling of the material by vacuum trucks but also the disposal of the sand and water after the separation process is completed. This adds significantly to the costs due to additional trucking and infrastructure required to perform the process. Furthermore, the waste sand still must be taken to a disposal site. Even though there is a total reduction in the volume of oil slop material because of the removal of oil and water, the cost savings on disposal do not offset the cost of the cleaning facility plus additional trucking costs incurred according to this process.
More commonly, the oil slop material is taken directly to a disposal cavern where all of the material is disposed of. This results in a complete loss of the oil present in the slop. Even though this procedure results in the complete loss of the oil in the slop, this route is still significantly cheaper than the first route involving the recovery of oil, due to the excessive handling and substantive costs associated with the cleaning facilities and disposing of the sand.
U.S. Pat. Nos. 6,074,549 and 6,527,960, both of Bacon et al., each disclose a process for separating oily films from sand particles. The processes each involve the use of a jet pump scrubber in a density classification tank at temperatures above 65° C.
The prior art also discloses the use of a fatty acid alkyl ester to improve recovery of oil from an oil reservoir. This process is disclosed, for example, in U.S. Pat. No. 6,776,234 of Boudreau and in published Canadian patent application 2,233,710 of Cioletti et al.